Many kinds of electrical apparatus, instrumentation, components, and the like are connected to a power supply and/or another device with a multi-conductor, flexible cable. Such a cable typically has a plurality of conductors which are in side-by-side, parallel, spaced relationship within a web of encapsulating insulation which is usually a thermoplastic material.
Each conductor may be formed from multiple, twisted strands of wire. In some applications, it is preferred to use only a single strand of wire for each conductor.
For example, a single, solid strand of wire is used for each of the four parallel conductors in a flat flexible cable provided with the blood pressure sensor system sold in the United States of America under the brand name Transpac.RTM. IV by Abbott Laboratories, Inc., One Abbott Park Road, Abbott Park, Ill., 60064-3500, U.S.A. The Transpac.RTM.IV blood pressure sensor system includes a blood pressure transducer system which is electrically powered and which generates an electrical signal with voltage corresponding to the pressure of the blood in the system.
The transducer system includes a silicon chip with a thin wall functioning as a pressure-sensitive diaphragm. The strain-responsive thin wall or diaphragm of the silicon chip defines a strain-responsive integrated circuit. One side of the thin wall or diaphragm is subjected to the blood pressure, and an opposite side or "back side" of the chip thin wall or diaphragm is sealed in a chamber. The chamber is in communication with a lumen or passageway extending through the flexible cable insulation in parallel relationship with the four spaced-apart, single strand wire conductors. The conductors provide power to the integrated circuit on the silicon chip and carry from the integrated circuit the generated signal which corresponds to the blood pressure.
For calibration purposes, before the system is connected to a patient, a vacuum (i.e., a reduced pressure) may be drawn with a suitable vacuum apparatus connected to the cable lumen. The exterior or back side of the integrated circuit chip diaphragm can thus be subjected to a predetermined reduced pressure while the side of the diaphragm that would normally be exposed to the blood pressure is at ambient atmospheric pressure. The pressure differential simulates an operating system pressure differential that would arise when the system is connected to a patient, and the patient's blood pressure acts upon one side of the diaphragm while ambient atmospheric pressure acts on the other side of the diaphragm.
In the Transpac.RTM.IV blood pressure sensor system, the ends of the cable conductors are electrically connected to the strain-responsive integrated circuit on the silicon chip diaphragm. The strain-responsive integrated circuit is a suitable bridge circuit which can function generally like a Wheatstone bridge circuit or similar circuit. At the other end of the cable, a connector is provided for releasably connecting the cable to a monitor unit which supplies power to the integrated circuit and which monitors the signal generated by the integrated circuit. The connector at the end of the cable is adapted to be received in a jack connected to the monitor unit. The cable end connector and jack are similar to a conventional telephone connector and jack, respectively, that are commonly used in the United States of America.
The Transpac.RTM.IV connector, like the telephone connector, accommodates four conductors in a cable. However, the four-conductor cable of the Transpac.RTM.IV system also includes the lumen extending parallel to the four conductors, and the connector at the end of the Transpac.RTM.IV system cable accommodates that arrangement. In addition, in the Transpac.RTM.IV system, each conductor comprises a single strand of wire rather than multiple, twisted strands of wire typically employed in telephone cables.
The lumen in the Transpac.RTM. system cable is accessible via an aperture through the cable insulation adjacent the connector, and the access aperture is normally sealed closed by a removable plug in a rubber boot which is disposed around the portion of the cable and connector.
In order to draw a vacuum in the lumen in the Transpac.RTM.IV system cable, there must be essentially no leakage within the cable along the four conductors. If conventional, multiple, twisted strand wire is used for each conductor, then air can leak along the twisted strands of each conductor into the evacuation chamber adjacent the exterior side or back side of the transducer. To prevent such leakage, the Transpac.RTM.IV cable system employs only a single strand wire for each conductor, and each single strand of wire is encapsulated by the cable insulation material along its length.
The connector at the end of the Transpac.RTM.IV system cable includes a housing for receiving an insulated end portion of the cable. The four spaced-apart, parallel, single strand conductors are each contacted by a separate one of four, gold-plated spades or contact terminals that are each pushed through the cable insulation so as to engage a single strand conductor. The opposite end of each spade contact terminal is exposed in a slot in the connector housing and is adapted to engage a mating contact in the receiving jack attached to the monitor unit.
While the Transpac.RTM.IV system spade contact terminals function generally satisfactorily, they suffer from disadvantages. In particular, carefully controlled manufacturing techniques must be employed to avoid misalignment between each spade contact terminal and the single strand wire conductor as the spade contact terminal is pushed through the cable insulation.
It is difficult to establish contact between the spade contact terminal and the single strand conductor owing to (1) manufacturing tolerance variations in the diameter of each single strand connector and in the spacing between the connectors within the cable, and (2) variations in the insulation which may cause the spade contact terminal to move slightly to one side or the other as it is pushed through the insulation.
It is possible for the conductor to be missed altogether by the spade contact terminal. In other cases, only a very slight contact may exist between the inserted spade contact terminal and the conductor. In still other cases, the conductor may be completely severed by the spade contact terminal. These conditions can result in poor, intermittent, or non-existent electrical connections. As a result, the assembly process must maintain extremely close tolerances, and quality control must be sufficiently rigorous to identify completed assemblies that do not meet operational specifications. Accordingly, it would be desirable to provide an improved connector which could accommodate less stringent manufacturing techniques. Such an improved connector should preferably be less dependant upon close component tolerances.
Further, such an improved connector should preferably eliminate, or at least substantially minimize, problems associated with the integrity of the electrical connection between the cable conductors and the jack into which the connector is inserted.
It would also be advantageous to provide an improved connector which would (1) reduce the number of electrical connection points (which are areas of potential failure), (2) reduce the cost of production by minimizing the number of components, and (3) eliminate the use of more expensive components (e.g., gold-plated spades or contacts).
It would also be desirable to provide such an improved connector for being readily incorporated in configurations that can be received in, and mate with, a standard telephone jack.
The present invention provides an improved connector which can accommodate designs having the above-discussed benefits and features.